Nitrogen addition and experimental drought simplified arthropod network in temperate grassland

Abstract

Abstract Biodiversity is threatened by global changes, but related research has focused primarily on species or functional group diversity, neglecting their interaction networks. The latter are particularly sensitive to global changes and essential for biodiversity maintenance. Furthermore, multiple global change factors are typically examined separately, rather than in concert which is more realistic in nature. To explore the responses of arthropod networks to multiple global changes, we conducted a field experiment in temperate grassland in northeast China, in which nitrogen (N) deposition, drought, snowmelt timing and their interactions were manipulated. We constructed and assessed networks of arthropod functional groups, and explored their responses to changes in plant communities and the abiotic environments. Nitrogen addition decreased arthropod network complexity because increased foliar N and simplified plant community strengthened trophic chains along a single pathway, weakening the net effect of other pathways. However, experimental drought decreased network complexity by filtering out plant species and changing micro‐habitats. While delayed snowmelt significantly increased arthropod abundance only in early spring, its interaction with N addition or with drought had various impacts on arthropod functional groups. Our results suggest that the interaction of arthropod consumers with plant species richness and with plant nutrients finally reduced the robustness, connectedness and function of entire species/functional group networks in response to global change factors. In conclusion, species loss and increasing plant nutrient concentrations are key factors simplifying networks under multiple global changes, and such simplification is likely to be strengthened if coupled with changes in micro‐habitats. Our study highlighted that the effects of multiple global change factors should be studied in concert, even though they occur in different seasons, so that their effects on ecological networks can be perceived as a panorama. Read the free Plain Language Summary for this article on the Journal blog.